The present invention relates to a vehicle having a thermoelectric generator.
As used herein, the term “thermoelectric generator” indicates a system which is in a thermal connection with a heat source and a heat sink and which generates an electric voltage or an electric current from the temperature difference while utilizing the “Seebeck Effect” known from physics. In principle, the thermoelectric generator is therefore a Peltier arrangement operating in a physically opposite manner.
A thermoelectric generator has two different semiconductor materials which, similar to the schematic diagram of FIG. 2, are mutually connected in a thermally and electrically conductive manner. When this pairing of materials is subjected to a temperature difference between a heat source or a heat sink, an electric voltage (thermovoltage) is generated between the two material elements. By combining a large number of such elements, economically usable electric power can be achieved by means of a correspondingly efficient heat source.
Currently, approximately ⅔ of the energy in the form of heat contained in fuel is emitted to the environment in the case of modern road vehicles having an internal-combustion engine. There have already been a large number of approaches relating to the utilization of this “waste heat”. In DE 10 2006 057 662.4, which is not a prior publication, a vehicle having a thermoelectric generator is described, which generator is arranged in the exhaust line and operates to convert a portion of the heat contained in the exhaust gas to electric energy. A large number of further publications relate to the utilization of energy contained in the exhaust gas, such as U.S. Pat. No. 4,673,863 A, DE 42 08 358 A1, DE 41 18 979 A1, JP 07012009 A, U.S. Pat. Nos. 5,625,245,6,028,263 A,5,974,803 and US 2003/0223919 A1, DE 100 41 955 A1, WO 2004/059138 A1, as well as WO 2005/020422 A1.
Furthermore, an arrangement is known from DE 10 2005 058 202 A1, in which waste heat of an engine is converted to electric energy by use of a thermoelectric generator, the thermoelectric generator being connected to the cooling water circuit of the engine.
It is an object of the invention to convert the residual heat stored in individual vehicle components to electric energy by use of a simply and compactly arranged thermoelectric generator, and to do so also when the vehicle is parked.
This object is achieved by a vehicle having a heat-emitting component and a thermoelectric generator, which has a heat-absorbing component thermally coupled with the heat-emitting component, and which generates electric energy from the temperature gradient between the heat-absorbing component and a heat sink. The thermoelectric generator is arranged directly on the heat-emitting component and is connected thereto in a thermally conductive manner. Advantageous embodiments and further developments of the invention are described herein.
According to the invention, a vehicle includes a “heat-emitting component” and a thermoelectric generator. The heat-emitting component may, for example, be the vehicle engine (internal-combustion engine) or its engine block or engine crankcase, the oil pan of the vehicle engine or another component of the engine that permits a good heat transfer. As an alternative, the heat-emitting component may also be a transmission, such as an automatic transmission, a manual transmission, an automated transmission, a transfer transmission, an axle transmission, or the like. The thermoelectric generator has a “heat-absorbing component” thermally coupled with the “heat-emitting component”. The thermoelectric generator generates electric energy from the temperature gradient between the heat-absorbing element and a heat sink. The heat sink may be formed, for example, by the ambient air (air stream) or by a coolant of a coolant circuit to which the heat-absorbing element is connected.
An aspect of the invention consists of the fact that the thermoelectric generator with its heat-absorbing component is arranged directly on the heat-emitting component and is connected with the heat-emitting component in a thermally conductive manner. A good heat transfer is thereby achieved in a simple manner between the heat-emitting component and the heat-absorbing component of the thermoelectric generator. Preferably, the mutually adjoining surfaces of the heat-emitting component and of the heat absorbing component are each produced from a material having a high thermal conductivity. The heat-absorbing element of the thermoelectric generator could, for example, be made of copper.
The electric energy generated by the thermoelectric generator can be used for charging an electric energy accumulator, for example, a battery or a capacitor, provided in the vehicle, but also for directly supplying current to diverse electric consuming devices or loads provided in the vehicle, such as the audio system, the air conditioning system, the blower, etc.
According to a further development of the invention, it is provided that the electric energy generated by the thermoelectric generator is utilized for keeping an electric energy accumulator, for example, a battery or a capacitor provided in the vehicle, warm after the internal-combustion engine has been switched-off. For example, an electric heating device may be provided which, after the vehicle has been switched off, is supplied with electric energy by the thermoelectric generator and heats, for example, the battery at least for a certain time period, or keeps it warm.
As an alternative or in addition, the electric energy generated by way of the thermoelectric generator after the switching-off of the internal-combustion engine can also be used for keeping certain components warm whose operating temperature is relevant with respect to consumption when the internal-combustion engine is started again. Thus, by use of the electric energy generated by the thermoelectric generator after the switching-off of the internal-combustion engine, for example, the engine oil, or the cooling water can be heated, or consumption-relevant components, such as the crankshaft, the valve gear, the pistons, etc. can be heated or kept warm.
In summary, the following advantages may be achieved by way of the invention.
(a) A portion of the heat, which is released during the driving operation by way of the engine surface into the atmosphere (ambient air), can be converted to electric energy. As a result, operation of the generator is reduced and fuel is saved, which improves the energy balance of the vehicle.
(b) After parking the vehicle, the engine will cool down over a period of several hours. The heat stored in the engine block is released into ambient air by way of radiation and convection. By way of the thermoelectric generator, a portion of the heat stored in the engine can be converted to electric energy also when the vehicle is stationary.
In comparison to conventional approaches, in which the thermoelectric generator is integrated into the exhaust line, clearly lower technical risk exists when the thermoelectric generator is mounted on the engine block, on the transmission case, or on the axle transmission casing.
Compared with a thermoelectric generator integrated in the exhaust line, in the case of an arrangement directly on the engine, slight voltage fluctuations occur because of the slight temperature fluctuations of the hot side, which reduces the technical expenditures for smoothing the electric voltage.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.